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Radio - JR & Spektrum DSM > Another AR7100R and another broken antenna

creightoncarr
Veteran
Location: Missouri City, Texas - USA

I'm on my third AR7100R - anyone who missed the earlier threads, the first two failed when the antenna broke off from the main receiver. After the first two incidents I opened the case on the third receiver and put a bunch of hot glue around the solder joint and the antenna to try and provide better vibration protection.

First ten flights or so were eventless. Went out this evening to get a couple flights on the Aurora with this receiver mounted in it, and about a minute or two into the second flight the helicopter started jumping around randomly (same thing happened with the first receiver when the antenna broke). Landed, brought it home, opened the case and here is what I found:

I'm three for three on these receivers now. As things would go, I happened to get a call this evening from someone very well respected in the heli community who told me that his team pilots have stopped using these receivers because one of them crashed as a result of this very problem. I don't feel comfortable posting names right now because I'm not sure whether this was passed along to me in confidence or not. Needless to say, I was starting to wonder what in world I could be doing wrong (I've never lost an antenna on any other receivers [OK, not true, back with the 72MHz receivers I had antennas rip out on crashes]) but at least now I know it's not just me.

It's too bad, the idea behind the receiver is great and I really wanted it to work out (obviously b/c I gave it three chances). Unfortunately, I don't think Spektrum did enough testing on this product before releasing it. Maybe future revisions will be better, but there really is no excuse for such a poor connection between the antenna and board. To all who decide to continue to use the AR7100R, I wish you the best of luck. For me, I'm not going to risk it anymore.

07-04-2008 04:49 AM

carcrasher
Key Veteran
Location: east coast

Good thing you were able to land it!

07-04-2008 04:57 AM

ez2bgman
Elite Veteran
Location: N'awlins, LA

Thanks for the heads up. I was thinking about getting one too. I think I will wait a bit and see what happens.

Gary
RJX of USA
Magnum Fuels
SwitchGlo
>Hot Girlz in da gallery<

07-04-2008 04:58 AM

HOMEPAGE

creightoncarr
Veteran
Location: Missouri City, Texas - USA

Here were the other two:

07-04-2008 05:15 AM

culverdan
Senior Heliman
Location: American Canyon,CA

This sucks

I was talking with creightoncarr or should say pming him about this rx as I just went out today and bought one. So here I am on the fence of what to do about it. I guess I could open the case and see if I could clear away some of that glue or just return it and get my money back an check out the 7100. Do you think they are having the same issues with it???? I was also wondering if setting this thing on two pieces of foam would help it out at all or atleast one. Just wondering did you have foam under it. I know I dont have any foam under my rx on my 600 kinda of dumb of me

.

Well I think I can fly it..............UH OH OOPS heres your heli.

07-04-2008 06:42 AM

opti
Senior Heliman
Location: clagiraba, queensland, australia

ive just fitted 2 to my vibes ,i carnt stop the antenna hitting the canopy,is that a problem?youve got me worried now.

07-04-2008 08:00 AM

creightoncarr
Veteran
Location: Missouri City, Texas - USA

Quote
Just wondering did you have foam under it

Mine were all mounted with two pieces of foam tape AND velcro (i.e. foam tape attached to radio tray, and velcro attached to top of foam tape and to receiver).

My antennas were not hitting the inside of the canopy.

07-04-2008 11:36 AM

Climax
Veteran
Location: West London, United Kingdom

Assuming that these are fatigue breaks caused by vibration, then supporting the entire length of the antenna in stiff-ish fuel tube might help. Just an idea...

07-04-2008 12:14 PM

HOMEPAGE

creightoncarr
Veteran
Location: Missouri City, Texas - USA

You mean like this:

Yep, that is how all of mine have been installed. They still failed. FWIW, the Aurora runs as smooth as can be - there are no abnormal vibrations. In my mind this is obviously a manufacturing problem, and one I am sure Spektrum will resolve with future revisions. For now though, I for one would not take the chance. It may work for you, or it may not, but is it really worth taking the chance? I highly doubt Spektrum will replace your heli if you lose it because the receiver takes a dump.

I should add that I don't know if it's the normal vibrations that nitro heli's suffer from that is causing the problems, or the way I fly the helicopter. This video is from one of the flights just a couple before failure: http://www.vimeo.com/1253566

Who knows, it may work fine for sport flying and mild 3D without hard stops and jerks. But then again, I don't think that was it was really designed for that as most of those type pilots aren't as concerned with running their servos unregulated and getting the absolute top performance out of them.

07-04-2008 12:29 PM

Climax
Veteran
Location: West London, United Kingdom

Wow, that's not good!

07-04-2008 12:55 PM

HOMEPAGE

steve9534
Key Veteran
Location: yakima, wa.

Antenna breakage

"That is how all of mine have been installed". Spektrum has had a known problem with antenna breakage, but you might consider that putting the tubing on the antennae just adds some extra weight to be worked on by the "G" forces when you fly. I honestly don't think that's your problem, though. I believe that mounting the Rx on the CF frames next to the motor is transmitting enough vibration that the antennas are breaking. The thin mounting tape you've used affords very little vibration protection and the CF frames are going to transmit the vibration of the motor to the Rx no matter how smooth it appears to be. I'm also curious as to why having one antenna break would cause glitching? There are four different antennas and one would hope that the other three would be sufficient to maintain radio contact??? steve.

07-04-2008 02:36 PM

creightoncarr
Veteran
Location: Missouri City, Texas - USA

Can't answer why one antenna breaking would cause a problem. There are only three antennas, however, as there is only one antenna on the main receiver. All I can say is that on two of the three that I've had break, the servos started bouncing around. I was still able to control the helicopter but it was jittery.

The fuel tubing was supported by the rubber boot and the not the antenna. It's stiff enough I'm pretty sure it wasn't putting any load on the antenna itself. I know I could wrap the receivers in foam for better vibration protection. FWIW, I have a number of R921's mounted the exact same way, some with hundreds of flights on them, on not a single antenna has ever come off - even after some pretty grueling crashes.

07-04-2008 03:07 PM

rscott
Heliman
Location: Cedar Rapids, IA

Is the end of the board where the antenna is attached fixed in the case so it will not vibrate?
It looks from the pictures and from looking at a receiver I have that the boards inside will vibrate around inside the case. This could be causing the antenna breakage. The end near the antenna should be attached better to the case. Possibly putting a small amount silicon between the boards and the case in several spots would stop the vibration of the boards inside the case.
I noticed on mine that the U4 on the bottom has a couple pins that have pressed into the support on the bottom of the case. If I use it this way, it looks like that might also cause problems down the road.
Bob

07-04-2008 03:25 PM

Mike545
Heliman
Location: gettysburg, pa

great and i just made the switch, keep us posted on whats the problem

07-07-2008 12:18 AM

floop
Senior Heliman
Location: Deptford - Southern, NJ

Has anyone had this happen with the regular AR7100? (Without governor)
I have 34 flights on mine with T-rex 600 and no problems yet but this is making me nervous..

IT's what I do.

07-07-2008 04:42 PM

Yug
rrProfessor
Location: UK. Herts

Hmmm, I was just considering getting the AR7100R to take advantage of it's power distribution features. Perhaps not just yet

Looking at your pics, I definately looks like vibration is the cause. As mentioned earlier, some silicone to aid supporting the PCB would be a good idea and perhaps some sleeving over the antenna from where it exits the PCB to where it exits the case.

Vegetable rights and Peace

07-08-2008 12:14 AM

altima1779
Senior Heliman
Location: Toledo, oh u.s

If anyone else is having this problem please post. I have one in my 600n and have not had a problem yet. I have a second one siting on bench waiting to go in my 90.I also wonder why the remote antenna does not pick up the lose of the main. I just got a ar7000 back from Jr that has an antenna issue that I did but notice but it was brougt to my attention

You have to start somewhere!

07-08-2008 02:50 PM

trunkmunki
Senior Heliman
Location: Bangor

Has anyone had any communication with Spektrum about this? If so, what have they said?

07-08-2008 04:40 PM

RAK402
Veteran
Location: Alhambra, CA

I assume that it is impractical to wrap the reciever in foam, like one would have done with an older, crystal type RX, due to the regulator having to disapate heat?

07-08-2008 05:54 PM

marked23
Key Veteran
Location: Lynnwood, WA

RAK,
Unlike other regulators where the entire system (including swash servos) is regulated, this internal regulator only has to power the rudder and gyro (and optionally the throttle servo). So with lower power throughput, it doesn't need cooling. There are no fins or anything designed for air cooling, so go ahead and wrap it.

-Mark

07-08-2008 06:02 PM

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Radio - JR & Spektrum DSM > Another AR7100R and another broken antenna

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